This invention relates to calculating display mode values.
A display streamer in a graphics processor requests display data from memory to be temporarily stored in a FIFO (first-in first-out) and continuously feeds the display data to a display engine. Any break or interruption in feeding the display data results in visual artifacts in the final output (display) on a display device, e.g., an analog cathode ray tube (CRT) monitor. Additionally, the memory is usually most efficient when providing data at a high rate while the graphics processor can usually only use data at a rate that is much lower than this high rate.
To eliminate these visual artifacts and increase efficiency, the display streamer may be programmed with a watermark value and a burst length value for each display mode supported by the graphics processor. A display mode can be, e.g., a combination including display device resolution, color depth or pixel depth, refresh rates, and system configuration. The watermark value represents a FIFO size and falls between the minimum and maximum size of the FIFO, usually expressed in quadwords (QW) that are blocks of eight bytes each.
When the amount of data in the FIFO drops below the watermark value for the current display mode, the display streamer requests more display data from memory. A display mode's burst length value falls between the minimum and maximum amounts of display data, usually expressed in QW, that the display streamer may request from memory at a time. Analytic models may be used to predict the watermark values and burst length values for each display mode. There are over one hundred display modes.